gravity hot water heat conversion

NHPluminator

Q = im going to have to replace an old gravity hot water boiler out... can i use circulators with this..? to convert it to forced.. the radiators are old steam single pipe...

it has 2 feeds and 2 returns size 3"....

Steamhead

?????????????????

"old gravity hot water boiler"

"the radiators are old steam single pipe"

Uhhhh, we need to know if it really is hot water or actually steam.....

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NHPluminator

Ummmm sorry i didnt realize i wasnt more spacific ..
no it is NOT steamm...hense the " gravity hot water"..
it USE to be steam but now its gravity hot water....

J.C.A._3

Generally,

Big pipe, small pump so as to not move the water too quickly through the large pipes.

Best advice I can give is to call the boiler manufacturer and ask for their advice on circulator sizing.Have the numbers ready for them because you will be asked! Been there, done that and learned the hard way the first time. Chris

Steamhead

If there's only one pipe connected to each radiator

it has to be steam. There's no way water can circulate in just one pipe. If the system has the old "Unique" radiator shutoffs, it can look like one pipe into the radiator (even though the valve has both supply and return connected to it), but the connection to the radiator is actually split down the middle to allow the water to circulate.

If you saw a boiler with no sight glass or low-water cutoff, it still can be steam- running in a VERY dangerous configuration.

If you're not sure what you have, that's why we're here to help. If you have a digital camera, take some pics and post them here. This would certainly help us identify the system.

JCA is right on the basic circ sizing for gravity hot-water conversions. You can find more info here:

http://www.heatinghelp.com/newsletter.cfm?Id=125



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Unknown

Yup, Chris is right

BUT, if I need questions answered, I call steamhead on these gravity conversions.

And Mike Thies is, how do we say, completely up to snuff on the subject, as well.

Not to snub anyone else, but this is a pet subject of a few folk here. They sure have done the homework on the matter.

Noel

NHPluminator

im not kidding ..its not steam it has a tridicator and it reads 18 psi.. hot water rise's thats how it works

Steamhead

OK, but

what part of it is "single pipe"? Is it a setup where the returns from the radiators feed right back into the same main that supplies them?

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NHPluminator

it is setup like this it has 2- 3" mains coming off the top of the boiler .. that loop to 1 side of the house each and return to the low rear of the boiler ... with 11/4" branch's to the radiators

Steamhead

How does the water

return from the radiators to the boiler? Are there return lines, and where do they connect?

If the radiators have feed and return lines to the single main, it's a very old "one-pipe gravity" system. If it is, you want to use a circulator with a very low flow rate so the water has a chance to rise into the radiators.

But despite the tridicator you found, that diagram sure looks like steam to me.

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